Searching for 1 apartment in Hamburg (Feb/Mar 13)

I am living in Hamburg since August, and I am currently searching for 1 apartment in Hamburg. The apartment should have Protected content (it is for 2 persons) and should be located preferably "close" to the city center (max. Protected content U/S Bahn. We will stay for at least 2 years in Hamburg, therefore we are searching for some place for a long time and not just for a few months.

Please let me know in case you are moving out or you know some place that is free,